Unnamed (upper South Fork, Otter Creek) (ARDF #ID063) Ag, Au

Unnamed (upper South Fork, Otter Creek)

Occurrence, Inactive

Commodities and mineralogy

Main commodities	Ag; Au
Other commodities	As; Hg; Sb; Zn
Ore minerals	iron oxide; unspecified sulfides
Gangue minerals	carbonate minerals; quartz

Geographic location

Quadrangle map, 1:250,000-scale	ID
Quadrangle map, 1:63,360-scale	C-4
Latitude	62.5451
Longitude	-157.57137
Nearby scientific data	Find additional scientific data near this location
Location and accuracy	This occurrence is on a southwest-facing ridge that overlooks the head of the North Fork of Otter Creek. It is about 1.3 mile northeast of hill 1861 and 0.8 mile west-northwest of hill 1953. The prospect is at an elevation of about 1,700 feet near the center of section 2, T. 28 N., R. 45 W., of the Seward Meridian. The location is accurate.

Geologic setting

Geologic description This occurrence is part of a gossan about a mile long that is developed on sulfide-bearing sandstone and siltstone of the Upper Cretaceous, Kuskokwim Group (Miller and Bundtzen, 1994; Miller, Bundtzen, and Gray, 2005). The gossan contains zones of quartz veinlets, silica-carbonate alteration in altered mafic dikes, and iron-oxide-cemented sandstone breccias. The orientation of the zone is uncertain. Grab samples contain up to 200 parts per billion (ppb) gold, 1,000 ppb silver, 1,900 parts per million (ppm) arsenic, 3,300 ppb mercury, 116 ppm antimony, and 300 ppm zinc (McGimsey and others, 1988).
Geologic map unit	(-157.573751901077, 62.5444181899317)
Mineral deposit model	Hot springs gold-silver? (Cox and Singer, 1986; deposit model 25a).
Mineral deposit model number	25a?
Age of mineralization	Unknown; altered dikes have not been dated.
Alteration of deposit	Silica-carbonate alteration in mafic dikes.

Production and reserves

Workings or exploration	Surface samples were collected by the Alaska Division of Geological and Geophysical Surveys and the U.S. Geological Survey in 1986 (McGimsey and others, 1988).
Indication of production	None

References

References McGimsey, R.G., Miller, M.L., and Arbogast, B.F., 1988, Paper version of analytical results, and sample locality map for rock samples from the Iditarod quadrangle, Alaska: U.S. Geological Survey Open-File Report 88-421-A, 110 p., 1 sheet, scale 1:250,000. Miller, M.L., and Bundtzen, T.K., 1994, Generalized geologic map of the Iditarod quadrangle, Alaska showing potassium-argon, major oxide, trace element, fossil, paleocurrent, and archeological sample localities: U.S. Geological Survey Miscellaneous Field Studies Map MF-2219-A, 48 pages; 1 sheet, scale 1:250,000. Miller, M.L., Bundtzen, T.K., and Gray, J.E., 2005, Mineral resource assessment of the Iditarod quadrangle, west-central Alaska: U.S. Geological Survey Miscellaneous Field Studies Map MF-2219-B, scale 1:250,000, pamphlet.
Reporters	T.K. Bundtzen (Pacific Rim Geological Consulting, Inc.), M.L. Miller (U.S. Geological Survey); and C.C. Hawley (Hawley Resource Group)
Last report date	5/19/2003